The present invention relates to clutch housings for use in transmissions and more particularly to a device for the retention of a snap ring within a clutch housing.
Clutch housings used in transmissions are generally cylindrical or cup-shaped and have an axis and an open end. A plurality of axially-extending inner planar portions and outer planar portions are alternately disposed about the periphery of the clutch housing to form splines. Angular planar portions are disposed about the periphery of the clutch housing between the inner and outer planar portions and are continuous with the inner and outer planar portions.
In operation, the clutch housing contains a plurality of annular driven clutch plates. Complementary teeth on the outer periphery of the driven clutch plates engage the interior splines of the clutch housing. Interposed between the driven clutch plates are a plurality of annular driving clutch plates having teeth on their inner periphery in engagement with the outer periphery of an interior hub, which is another splined clutch housing. When an axial engaging force is applied to the clutch plates, friction between the driving and driven clutch plates transmits torque from the internal hub to the clutch housing. The torque capacity of the clutch is proportional to the number of pairs of surfaces in contact; i.e., increasing the number of clutch plates in the clutch housing proportionally increases the torque capacity of the clutch.
The axial engaging force is imparted axially toward the open end of the clutch housing. In order to retain the clutch plates within the clutch housing, a snap ring is secured within the inner-periphery of the clutch housing between the clutch plates and the open end of the clutch housing. Various devices and methods have been used to secure the snap ring within the clutch housing. However, the axial engaging forces acting upon the clutch plates and snap ring are high, especially in heavy duty applications. This has required the placement of the snap ring at an increased distance from the open end of the clutch housing, in an effort to provide sufficient strength from that portion of the spline between the snap ring and the open end. Nevertheless, known clutch housings experience failure when the axial engaging forces cause the splines to be "peeled back" from the snap ring to the open end of the clutch housing. In particularly heavy duty applications such as in heavy equipment where the clutch housings are subjected to high stress, the clutch housings have required the use of an external reinforcement band welded about the outer periphery of the open end of the clutch housing in order to prevent failure. However, the external band interferes with the engagement of the external splines with other components and can interfere with the assembly of the clutch housing into the transmission. The external band also increases the cost of manufacturing the clutch housing and the total weight of the clutch housing.
One known clutch housing for use in a transmission retains the snap ring within a snap ring groove formed in the inner planar portions of the clutch housing. The snap ring groove is formed by machining slots, generally the thickness of the snap ring, across each of the inner planar portions around the inner circumference of the clutch housing. However, this method of machining the slots in the inner planar portions is expensive, and the removal of material from the splines weakens the clutch housing, causing failure of the clutch housing as described above or requiring the use of the aforementioned external reinforcement band.
Another known method for forming a snap ring groove is disclosed in U.S. Pat. No. 4,014,619, the assignee of which is the assignee of the present invention. In that method two parallel lances are formed across each inner planar portion. The material between the lances is then displaced radially outwardly to form the snap ring groove. However, the spline is weakened by the cuts which extend across each spline. In order to prevent the failure of the clutch housing, it is necessary to increase the distance of the snap ring groove from the open end of the clutch housing and/or to provide an external reinforcement band around the outer circumference of the open end of the clutch housing.
In another known method for forming a snap ring groove, disclosed in U.S. Pat. No. 4,997,073, a single cut is made entirely across each inner planar portion. Below the cut, a section of the inner planar portion is deformed radially outwardly of the clutch housing. The section above the cut (toward the open end of the clutch housing) is not deformed, thereby exposing an edge. The radially outwardly deformed sections of the inner planar portions form a snap ring groove on the inner circumference of the clutch housing. The forces on the snap ring bear on the edge of the non-deformed section. The cut across the entire inner planar portion weakens the spline and the clutch housing, requiring the placement of the snap ring at an increased distance from the end of the drum and/or the use of an external reinforcement band to prevent failure.
In another known method for retaining snap rings, disclosed in U.S. Pat. No. 3,922,932, an orifice is formed substantially across each of the outer planar portions. Material of the outer planar portion is displaced radially inwardly of the drum. The inwardly displaced material is used to retain the snap ring. The clutch housing formed by this method is weakened by the removal of material adjacent the snap ring. It is therefore necessary to retain the snap ring at a substantial distance from the open end of the clutch housing and/or use an outer reinforcement band around the open end of the clutch housing to prevent "peeling back" of the spline. Further, the removal of material adjacent the deformed portion is expensive.